Exploring, drilling, completing, and operating hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of these expenses, added emphasis has been placed on well access, monitoring and management throughout its productive life. Ready access to well information as well as well intervention may play critical roles in maximizing the life of the well and total hydrocarbon recovery. As a result, downhole tools are frequently deployed within a given hydrocarbon well throughout its life. These tools may include logging tools to provide well condition information. Alternatively, these tools may include devices for stimulating hydrocarbon flow, removing debris or scale, or addressing a host of other well issues.
The above noted downhole tools are generally delivered to a downhole location by way of a well access line, such as a wireline cable, drill pipe, coiled tubing, slickline, etc. Regardless, once positioned downhole at the end of the well access line, a well application may be employed by such a tool. A winch or other appropriate surface equipment may then be employed to withdraw the well access line and tool from the well. However, in many cases the tool may be stuck in place downhole. This may be due to the presence of an unforeseen obstruction, unaccounted for restriction, differential sticking of the tool against the well wall, a malfunctioning tractor, or a host of other reasons. Indeed, with the presence of increasingly deeper and more deviated wells, the likelihood of a downhole tool becoming stuck merely due to the depth and architecture of the well alone is increased.
Regardless of the particular reason for the sticking of the downhole tool, continued efforts to withdraw the line may lead to line or tool damage. Additionally, the risk of breaking the line at some, seemingly random, intermediate location and leaving potentially several thousand feet of line in the well may be of concern. Thus, in order to help avoid a circumstance in which the line is broken, a release mechanism is generally incorporated into the assembly which accommodates the downhole tool. Therefore, the assembly may be broken apart at a known location and surface equipment employed to pull the line out of the well, leaving only the downhole tool and part of the broken assembly behind. A subsequent fishing application may take place in order to dislodge and retrieve the tool and assembly portion.
A common release mechanism involves incorporating a mechanical “weakpoint” or separable housing into the noted assembly. The weakpoint may be broken once a predetermined load is applied as a result of the axial force of pulling on the line from surface. Unfortunately, employing a weakpoint in this manner may still lead to some degree of damage to the tool, line or tractor where utilized. For example, in an application where the weakpoint is broken in a horizontal well section several thousand feet below the oilfield surface, the line may react in a sudden slingshot fashion. That is, the line may snap back with significant force, perhaps damaging itself, the tractor, or high dollar tools such as sophisticated imaging or other measurement equipment.
In order to minimize potential damage and unpredictability of weakpoint release mechanisms, an electronically controlled release device (ECRD) may be utilized. That is, rather than rely on the breaking of a tensile stud through mere force as in the case of a weakpoint assembly, an electronic actuator of the assembly may effect release in response to a signal sent from equipment at the oilfield surface. Thus, a more controlled release may be achieved.
The controlled release via the ECRD allows the operator to even introduce a degree of slack in the line in advance of signaling the release. Thus, in theory, when the release occurs, the line is unlikely to react in the slingshot manner noted above. In fact, current ECRD designs inherently require that the load on the assembly via the line be substantially under 150 lbs. or so in order to ensure that the release takes place. This is due to internal interaction of release components which naturally grip one another and discourage release where a significant axial load is present on the line. More specifically, a significant axial load on the line may translate to a radial load on collet fingers of one half of the assembly which secure an actuator rod of another half of the assembly, thereby preventing release even where such has been signaled from surface.
Unfortunately, the safety measure of preventing release in circumstances of high axial load renders the ECRD unreliable where the operator's ability to reduce the load is compromised. For example, where an application involves tractoring the assembly and tools through a horizontal well section, a resultant high tension sticking may leave the operator unable to alter the line tension. That is, even where the operator introduces additional line to the well it may very well collect at the heel of the horizontal well section. Thus, the tension on the stuck portion of the line may remain high. As such, even where signaled to release, the mechanical design of the ECRD may prevent it from allowing the release to occur. As a result, the safety advantages of controlled release through the ECRD are often foregone where horizontal or highly deviated wells are involved.